Multiprotocol label switching (MPLS) is a scheme in high-performance telecommunication networks which directs and carries data from one node to the next node. The multiprotocol label switching mechanism assigns labels to data packets. Packet forwarding decisions from one node to the next node are made solely on the contents of the label for each data packet, without the need to examine the data packet itself.
Generalized Multiprotocol Label Switching (GMPLS) is a type of protocol which extends multiprotocol label switching to encompass network schemes based upon time-division multiplexing (e.g. SONET/SDH, PDH, G.709), wavelength multiplexing, and spatial multiplexing (e.g. incoming port or fiber to outgoing port or fiber). Multiplexing, such as time-division multiplexing is when 2 or more signals or bit streams are transferred simultaneously. In particular, time-division multiplexing (TDM) is a type of digital multiplexing in which 2 or more signals or bit streams are transferred simultaneously as sub-channels in one communication channel, but are physically taking turns on the communication channel. The time domain is divided into several recurrent timeslots of fixed length, one for each sub-channel. After the last sub-channel, the cycle starts all over again. Time-division multiplexing is commonly used for circuit mode communication with a fixed number of channels and constant bandwidth per channel. Time-division multiplexing differs from statistical multiplexing, such as packet switching, in that the timeslots are returned in a fixed order and preallocated to the channels, rather than scheduled on a packet by packet basis.
Generalized Multiprotocol Label Switching includes protection and recovery mechanisms which specifies predefined (1) working connections within a shared mesh network having multiple nodes and communication links for transmitting data between the nodes; and (2) protecting connections specifying a different group of nodes and/or communication links for transmitting data in the event that one or more of the working connections fail. In other words, when a working connection fails, the Generalized Multiprotocol Label Switching protocol automatically activates one of the protecting connections into a working connection for redirecting data within the shared mesh network.
However, the protection and recovery mechanisms defined in GMPLS have overlooked a number of issues when scaling to large optical shared mesh networks including switch over latency, and predictable protection. Predictable protection allows recovery in a fixed period of time. In the context of optical shared mesh networks using GMPLS protocols, there is no guarantee that a recovery will be within a fixed period of time. With respect to switch-over latency, in shared mesh network protection schemes, the protecting connections require explicit activation on the nodes during a traffic recovery procedure for redirecting data to the protecting connection. Activation using standard GMPLS signaling may take seconds, if not longer, to propagate and process, and thus may not be acceptable in shared mesh networks operated by a carrier. This is because GMPLS routes messages using an IGP (interior gateway protocol) protocol using flooding to notify all other known nodes of any network changes to the nodes. Flooding is a typical mechanism used in mesh networks to send a message simultaneously to all known nodes in the mesh network. With respect to predictable protection, shared resource availability information is not normally flooded due to scalability concerns because in a given mesh network, the amount of shared resource information which needs to be flooded could be very large, i.e., (number of nodes+number of links+number of Shared Risk Link Groups)*number of communication links. In GMPLS, nodes are assigned into Shared Risk Link Groups and a risk factor is assigned to each of the Shared Risk Link Groups. Nodes within the Shared Risk Link Groups are also notified of a failure which increases the amount of information to be shared. An alternative to flooding is through trial-and-error mechanisms where nodes automatically try to solve the failure through setting up alternative paths, such as crankback. Crankback is a mechanism used by networks to overcome failures and reduce flooding. In particular, crankback is used when a node along a selected connection cannot accept the request, the node automatically attempts to discover an alternative path to the final destination. In any event, the operators need to be aware of usable protecting connections in order to provide predictable traffic protection.
Traffic protection and recovery in shared mesh networks can be categorized in three general areas: “Cold standby”; “Hot standby” and “Warm standby”. Cold standby refers to a mechanism where the nodes will compute a new route upon the detection of a connection failure and then configure new connections to implement the new route. A delay associated with such computation and configuration may be in the range of seconds, which is not acceptable in many service provider networks. However, many IP shared mesh networks have adapted the cold standby approach.
Hot standby refers to a mechanism where a node within the shared mesh network will automatically provision at least one protecting connection to a working connection. In the event of network failure, user traffic can be directed to the protecting connection without additional configuration. The SONET APS scheme follows the hot standby approach and establishes a protecting connection and a working connection in parallel. In the SONET APS scheme, the working connection is used to carry user traffic at any given time. When the working connection has failed, the protecting connection will start to pick up user traffic with less delay than the cold standby mechanism. However, a drawback to the hot standby mechanism is that the protecting connections may consume too much network resources and may not be practical in many networks.
Warm standby is a mechanism where a node within a shared mesh network configures one or more protecting connections prior to a failure of a working connection without consuming additional network resources. In the warm standby mechanism, one of the nodes referred to as a “headend” node will transmit “wake-up” messages to pre-established nodes identified as part of the protecting connection to activate the protecting connection. The GMPLS protocols utilize the warm standby mechanism. Though the warm standby mechanism has the advantage of improved resource utilization, the current specification for GMPLS has two key drawbacks: (a) the activation utilizes the GMPLS routing and signaling protocols which are run by the control plane and which result in significant and unacceptable delays and (b) there is no scalable mechanism for the operators to be aware of the availability of the protecting connections.
The presently disclosed and claimed inventive concepts are preferably developed on top of the warm standby mechanism described above and eliminate the described drawbacks.